// Shamelessly copied and modified from Rob Hart's instructional code, which itself was shamelessly copied and modified from the code of Neil Gershenfeld.
//
//
// Button       PA2 (pin 11).
// Red LED      PA3 (pin 10).
// Green LED    PB2 (pin 5). Also OC0A.
// Blue LED     PA7 (pin 6). Also OC0B.
//
// See page 50 of Elliot William's Make: AVR Programming book for a rundown on PORTx, DDRx, and PINx registers.


#include <avr/io.h>       //this includes all definitions of registers and bits of registers, including pins and port names.

#define output(directions,pin) (directions |= pin) // set port direction for output
#define input(directions,pin) (directions &= (~pin)) // set port direction for input
#define set(port,pin) (port |= pin) // set port pin
#define clear(port,pin) (port &= (~pin)) // clear port pin
#define pin_test(pins,pin) (pins & pin) // test for port pin
#define bit_test(byte,bit) (byte & (1 << bit)) // test for bit set

#define input_port PORTA		   // The button is on port A
#define input_direction DDRA	 //  DDRA defines input/output for port A
#define input_pin (1 << PA2)	 //  The button is on pin 2 of port A    (1<<PA2) = (1<<2) = 0b00000100
#define input_pins PINA			   //  PINA is the register that is read to detect input high or low.
#define output_port_RB PORTA		   //  port A will be used for the Red and Blue LEDs
#define output_direction_RB DDRA	 // DDRB defines input/output for port A
#define output_pin_R (1 << PA3)
#define output_pin_B (1 << PA7)
#define output_port_G PORTB		   //  port B will be used for the Green LED
#define output_direction_G DDRB	 // DDRB defines input/output for port B
#define output_pin_G (1 << PB2)



int main(void) {
   //
   // main function.
   //

   // initialize pins

   output(output_direction_RB, output_pin_R);        //  set output for Red LED pin.
   output(output_direction_RB, output_pin_B);        //  set output for Blue LED pin.
   output(output_direction_G, output_pin_G);        //  set output for Green LED pin.
   set(input_port, input_pin);                  // turn on internal pull-up
   input(input_direction, input_pin);           // set button pin for input.
   
   // main loop

   while (1) {

    if (!pin_test(input_pins,input_pin)) {       //test button pin.
      	clear(output_port_G,output_pin_G);
        clear(output_port_RB,output_pin_R);
        clear(output_port_RB,output_pin_B);     //  if button not pressed, pin is LOW - turn off.
    } else {
        set(output_port_G,output_pin_G);
        set(output_port_RB,output_pin_B); 
        set(output_port_RB,output_pin_R);       //  if button is pushed, turn pin HIGH.
        }
      }
   }